The invention relates to a trans-platinum based compound, to a diagnostic kit comprising said compound, and to a method for labeling a bio-organic molecule wherein use is made of said compound.
Platinum (coordination) compounds have been considered interesting molecules for a very long time. For a review of these compounds and their uses we refer to Reedijk et al. (Structure and Bonding, 67, pp. 53-89, 1987). Especially cis-platinum has received a lot of attention as an anti-tumor drug. This anti-tumor reactivity of platinum compounds originates from their having at least two reactive groups (preferable cis-oriented towards each other), which make it possible to cross-link DNA molecules, thereby inhibiting the replication of these DNA molecules.
A different use of cis-platinum compounds has been described in European patent application No. 95201197.1. Herein a method is disclosed for linking bio-organic molecules and labels through cis-platinum compounds, of which two coordination sites are occupied by two ends of a stabilizing bridge, such as an ethylene diamine group.
These known cis-platinum compounds are suitable for linking labels to several kinds of bio-organic molecules. Examples are (poly)-peptides, polynucleic acids and nucleotides.
The labeling of polynucleic acids, such as DNA molecules, is desirable for applications in fields such as recombinant DNA technology. In many cases, however, one wishes not to label the nucleic acid macromolecule, but to label a certain nucleotide and enzymatically build this into a polynucleic acid. This way, the location of the label on the resulting polynucleic acid can be influenced, which is not possible when a label is attached to the macromolecule.
It has been found, however, that nucleotides linked to a label by cis-platinum linkers are not satisfactorily built in into DNA molecules by DNA polymerase, if at all. Therefore, in order to use a cis-platinum linker for obtaining a labeled DNA molecule one has to label the macromolecule.
The available alternatives for labeling a nucleotide, which can be incorporated into a polynucleic acid are the more conventional methods of labeling. However, these conventional methods also have a major disadvantage as they are not suitable for labeling any nucleotide. In some cases, for instance when only a few residues of a certain nucleotide are present in a certain polynucleic acid, or when the terminating nucleotide residue of a polynucleic acid is to be labeled, it is desired to be able to label any nucleotide.
An example of such a conventional method has been described by Dale et al., Biochemistry, 14, (1975), 2447-2457, which method involves direct covalent mercuration as a labeling technique. Dale et el. report that cytosine and uracil may be mercurated at their C5-position under mild conditions. However, they also report that for adenine, thymine and guanine bases negative results were obtained.
Thus, there is a need for a universal linking system, which is excellent for linking labels and bio-organic molecules, including all different nucleotides, and which also makes it possible to enzymatically build in any nucleotide labeled through said linking system in a polynucleic acid in an efficient manner.